Muffler



Nov. 10, 1959 R. G. BARNES MUFFLER Filed April 13, 1953 I United StatesPatent T 2,912,063 MUFFLER I Ralph Glenn Barnes, Dayton, 'OhioApplication April 13, 1953, Serial No. 348,435 1 Claim. Cl. 181-66) Thisinvention relates to mufilers and the like as used, for example, inconnection with internal combustion engines to reduce noise involved inthe discharge of exhaust gases.

A muflier in accordance with the instant invention is characterized byhigh efliciency with a small compact construction. It is, therefore,especially suited for use on contractors equipment, such as compressorsand engine operated tools.

The prior development of mufflers has been directed for the most part atremoving the cause of the objectionable noise. This has been done bymeans of baffies and other obstructions that build up a back pressureand cause the exhaust to enter the silencing device against an air orgas cushion. Back pressure causes loss of power by preventing thoroughscavenging of the burned gases. Also, heat is retained which isdetrimental to the valve structures. In small horsepower engines, suchas are used on contractors tools, these disadvantages, of silencingfrequently are thought to outweigh the benefits thereof, with the resultthat no muflling or silencing is provided.

The instant invention proposes a silencing means which functions withoutimposition of back pressure and which is only partly aimed ateliminating noise producing gas pulsations. In this invention suchsounds are allowed to occur within an expansion chamber and then thegases are led out to the atmosphere without resistance. At the sametime, sound within the chamber is mufiled by multiple surrounding airchambers.

The object of the invention is to simplify the construction as well asthe means and mode of operation of mufflers as disclosed 'herein,whereby such devices may not only be economically manufactured, but willbe more eflicient and satisfactory in use, adaptable to a wide varietyof engines, having relatively few parts and b unlikely to get out ofrepair.

Afurther object of the invention is to obtain a muffler providingeffective silencing without material loss of engine power. Anotherobject of the invention is to obtain a muflier of small, compact designespecially suited for use in connection with power tools and the like,although not necessarily limited thereto.

A further object of the invention is to obtain a muffler providing forsimple, economical manufacture according to structural principles withinwhich the construction may be varied to meet space and other specialrequirements.

Still another object of the invention is to provide in a muffiei; novelprinciples of an expansion chamber and a circuitous outletpassagetherefrom having a duofunctional character, whereby exhaust gases maybeconducted to atmosphere without imposition of back pressure and in amanner to reduce and smooth out pulsations.

A further object of the invention is to provide a muffler possessing theadvantageous structural features, the

inherent meritorious characteristics and the mode of operation hereinmentioned.

With the above primary and other incidental objects in view as will morefully appear in the specification, the invention intended to beprotected by Letters Patent consists of the features of construction,the parts and combinations thereof, and the mode of operation, ashereinafter described or illustrated in the accompanying drawings, ortheir equivalents.

Referring to the accompanying drawing, wherein is found the preferredbut obviously not necessarily the only form of embodiment of theinvention:

Fig. 1 is a perspective view of a mufller in accordance with the instantinvention;

Fig. 2 is a view of the mufller of Fig. 1 in cross section;

Fig. 3 is a view in cross section of a muflier like that of Figs. 1 and2, but illustrating an alternative spark arresting feature ofconstruction;

Fig. 4 is a view in longitudinal section of the muffler of Figs. 1 and2, taken substantially along the line 44 of Fig. 2;

Fig. 5 is a view of a mufiler which is like those of Figs. 1 to 4 bututilizes a multiple winding instead of a single winding principle ofconstruction;

Fig. 6 is a fragmentary view, in longitudinal section, of a muffier likeany of those of preceding views, incorporating an alternative spacerarrangement; and

Fig. 7 is a view, in longitudinal section, of an air intake silencerconstructed in accordance with the instant invention.

Like parts are indicated by similar characters of reference throughoutthe several views.

Referring to the drawing, the embodiments of Figs. 1 to 6 disclose amuffler of a kind having particular application to internal combustionengine operated tools, although the same principle may be utilized inconstructing mufflers for other types of internal combustion engines. InFig. 1 an extension pipe 10 receives the gases of combustion from theengine and delivers them to the muflier, indicated at 11, which ismounted on or unitarily joined to the pipe 10.

The mufiler 11 comprises spaced apart end plates 12 and 13 and a coil 14installed between the plates. The coil 14 presents a circuitouspassageway for the escape of exhaust gases admitted through pipe 10,such passageway terminating in an outlet 15 defined by an outturned lip16 at the external extremity of the coil.

The muffler shown in Fig. 1 is further illustrated in Figs. 2 and 4. Asmay be there seen, the coil 14 is made of a single winding of acontinuous strip of sheet metal. The several convolutions of the coilare closely spaced in a relatively wide diameter area so that a largeinternal chamber 17 is defined. The ends of chamber 17 are closed by theplates 12 and 13, in the latter of which is an axial opening 18communicating with the pipe 10. In the illustrated instance the pipe 10and plate 13 are made an integral, one-piece construction.

The opening 18 accordingly serves as the inlet to the mufiler,discharging the exhaust gases directly into the chamber -17. Chamber 17,it will be observed, is substantially greater in cross-sectional areathan the inlet 18. As a result, the chamber 17 functions as an expansionarea offering no opposition to the free flow of gases from the engine.

The several convolutions of the coil 14 define a spiral passageway 19,the outlet 15 of which has previously been referred to. The inlet 21 ofthe passageway is marked by the inturned inner extremity 22 of the coil14 and communicates directly with the'expansion chamber 17. Thus chamber17 is in continuous communication with the atmosphere through passageway19 and the gases Further, the explosive sound of discharge in thechamber 17 is .muflied by the multiple surrounding air layers pro videdby the several convolutions of the coil.

The passageway 19 extends approximately the full Width of the stripwhich forms coil=l1 4. Its height, as determined by the spacing betweenthe convolutions of the coil 14 is relatively short. Dimensionally,therefore, the'passageway 19 may be described as broad. andflat. Incross-sectional area'itis approximately the same as or slightly greaterthan the area of inlet 28. T he rate of flow through the inlet 18and'through the passageway 19 will, therefore, be about the sarnewithchamber 17 providing an intermediate area of expansion positivelyprecludingthe creation of back pressure.

The dimensions of thepassageway "19 are uniform throughout its length.Establishing and maintainingsuch uniformity is a pair of spacers 23, oneof which is located adjacent each side edge "of the coil 14. In theembodiment under discussion the spacers 23 are round Wires which areplaced on the'sheet metal strip prior to .coiling and then woundsimultaneously with the winding of the coil. When the coil has beenwound, with the spacers 23 in place,'the assembly comprising the coiland spacers is subjected to a brazing or welding operation uniting eachspacer convolution to adjacent coil convolutions. A permanent coilformation as illustrated is thus achieved, and, additionally, thespacers are made to function as side walls for the passageway 19. As apart of the same welding or brazing operation :above described,'the endplates 12 and 1-3 may be secured to the side edges of the coil 14.

By reason of its uniform dimensions, the passageway '19 conducts thegases in a thin sheet through the unit,

smoothing out the pulsations and soadding to the silencingcharacteristic obtained by enclosing chamber 17 with multiple sounddeadening air spaces.

A number ofvariations in theprinciples above described are possible.InFig. 3, for example, a,sparlr arrester feature is added to themuffler. In this instance, a coil-24 has its outer extremity 25 turnedat a tangent to the body of the coil and then bent inward toward theaxis of the coil. Fastenedon the bent-in end and projecting' to eitherside thereof is a piece 26 defining with the extremity 'of the coil apocket 27 and defining with the outer convolution of the coil anoutletopening'i2t3. The exhaust gases will tend to flow first intothepocket 27 and then around the baffie-like projecting end. of piece 26to outlet-28. Burning carbon particles entrained in the gases will betrapped and extinguished in the pocket27.

In another modification, multiple strips of sheet metal are used tomaintain the proper ratio of ou-tletto inlet without lengthening theunit out of proportion .to space requirements, and to maintain anexpansion chamber of adequate size. According to this embodiment of theinvention, illustrated in Fig. 5, a coil 29 is made up of a-plurality ofsheet metal strips, and a corresponding number of spacers, arranged insuperimposed relation and Wound "together as in the embodiments of Figs.2 and 3. In this instance, however, three parallel passageways 31, and33are formed in the coil, each having its own inlet and outlet.

With regard to the spacers '23 of Figs. 2 and 4, similar spacers may beused in the other of the described embodiments. in any of the severalforms of the invention a different kind of spacing means may be used,for example that shown in Fig. 6. Here, the edges of the metal stripdefining a coil 34 are turneddown and inward, forming spacer channelmembers 35. According to this conception, therefore, the spacers are anintegral part of the coil and, of course, the simultaneous winding ofthe coil and spacers is facilitated.

The construction disclosed is useful as an airintake silencer, as wellas a muffler. An adaptation of this kind i A is shown in Fig. 7 whereinthe unit includes a coil 36 and spacers 37 defining a passageway 38communicating with the atmosphere and with an internal chamber 3 9. Thechamber 39 is closed by end plates 41 and 42 in the latter of which isan opening 43. In this instance a large expansion chamber isnotlimportant to operation of the device. Since the constructionof theinvention permits chamber 39 to be large in area, however, advantage maybe taken ofrthistormount an air ,,cleaner-cartridge 44 between theplates,4-1. and 42in such position that air passing to orfrom'the opening 43is compelled to pass through the cartridge.

=It will be apparent that other embodiments of the invention arepossible, including such obvious modifications as various combinationsof the features illustrated. Further, the shape of the coil may be otherthan round, for example oval. Also, it may in some installations bedesirable, 'on account .of spaceilimitations, to project an inletopening'laterally through the coil instead 'of' axially through anendplate.

' From theabove description it will'be apparent that there is thusprovided a device of the characterdescribed possessingtheparticular'features of advantage before enumerated as desirable, butwhich obviously is susceptible of modification in its form, proportions,detail construction and arrangement 'of parts Without departing from.the principle involved or sacrificing any of its advantages.

While in order tocomply with the statute the invention has beendescribed in language more or less specific as to structural features,it is to be understood that the invention is not limited .to thespecific features shown, but that the means and construction hereindisclosed comprise but one of several modes of putting the inventioninto effect.

7 Having thus described my invention,I claim:

A muffier for internal combustion engines includinga coil presenting aspiral passageway of substantiallyuniform cross-section, a centralexpansion chamber surrounded by said coil, means for closing theopposite ends of said" chamber, means connected to one of said closingmeans defining an opening therein to said chamber, the

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2,499,018 "Christiano et al Feb. 28,1950 2,557,236 Sebok June- 19, 19512' FOREIGN PATENTS "289,657 England May 3,1928

